Boats are usually taken out of the water during extended periods of non-use. Removal from the water is expensive for boats that are to large to be carried on a trailer pulled by a small truck or car. Removal as well as return to the water may have to be scheduled weeks or even months in advance. As a result a boat is often unavailable for use on days when the weather is excellent for boating.
Boats are often left in the water during periods of non-use of a few weeks. Contaminants in the water can stick to and stain surfaces of the boat hull and keel. Various water borne organisms can attach to the hull, grow for periods of time and damage the hull and keel surfaces.
Inflatable airbags have been used to lift the hull of boats above the surface of the water. These airbags have not however lifted the keel of a sailboat out of the water. The rudder and prop of motorboats may also remain in the water. Sailboats with a fixed keel would be unstable if the hull and the keel were both lifted above the water by airbags.
Flexible containers have been employed to receive the submerged surfaces of ocean going ships. These containers receive chemical that kill marine life attached to the ship hull. Pumps are provided to pump water and chemicals into and out of the container. Following the chemical treatment, the ship is returned to service. The system is for quick treatment to remove marine life from a ship hull. Damage to the hull has most likely occurred prior to chemical treatment. The pumps and chemical storage tanks are on a barge that has substantial size. Two small boats are used to pull one of the containers from the barge. Multiple motors are required to power pumps, wenches, screws and other portions of the system. Such systems are clearly designed to periodically treat the hulls of a number of ships each year.